Pulsed eddy current: Finding corrosion independently of transducer lift-off

The pulsed eddy current (PEC) technique holes the potential of becoming the primary means of detecting corrosion in multi-layer structures. However, it is still considered an experimental technique because there are stumbling blocks that must be overcome before it finds acceptance as a field application. In particular, it is necessary to be able to interpret the transient response and distinguish between transducer lift-off, defect locations, and defect size when these effects occur simultaneously. Thus far, most researchers in pulsed eddy currents have not considered lift-off variations in their studies. This parameter is kept constant as it complicates the analysis of pulsed eddy current transient responses. However, lift-off variations will be encountered during field inspections. This paper takes this issue into consideration. Specifically, the paper details an inspection technique which enables the positive identification of corrosion in a multi-layer structure. Moreover, the proposed technique provides a quantitative evaluation of material loss which is independent of lift-off variations.